\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\setCJKmainfont{Noto Serif CJK SC}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usepackage{wasysym}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes,}
\begin{document}
\small
\begin{tikzpicture}[>=latex,scale=1.0]
  \draw [fill=cyan!40] (-2,0) arc (180:360:2);
  \draw[->, very thick] (0,0)--(20:1.5); \draw[very thick] (0,0)--(20:2.2)node[above]{折射光线};
  \draw[->, very thick]  (0,0)--(-45:1.5); \draw[very thick]  (0,0)--(-45:3)node[below]{反射光线};
  \draw[very thick] (0,0)--(225:3);	\draw [<-,very thick](225:1.5)--(225:3);	
  \node at (-1,1){空气};
  \draw (-2,0)--(2,0);
  \draw[dashed] (0,-1)--(0,1);
  \node at (225:3.25){\sun};
  \node at (225:3.25)[below right]{光源};
\end{tikzpicture}
\end{document}